Tilly Ramsay‘s Any Fish Pie

Method

1. Heat your oven to 200°C/180°C fan/gas mark 6.
2. Peel and cut the potatoes into quarters then put them into a large saucepan. Cover them with cold water and put the pan over a medium heat. When the water is boiling, turn down to a simmer and let the potatoes cook for 15 to 20 minutes until they are very soft.
3. Drain the potatoes in a colander, then put them back into the pan and mash them with a potato masher. Add the butter and milk to the pan and mash again until the potatoes are lovely and smooth.
4. While the potatoes are cooking, slice the spring onions into small rings. Then chop the parsley with a large knife or in a mug with a pair of scissors. 
5. Grate the Cheddar cheese, being careful not to grate your fingers!
6. Place the flame-proof casserole dish over a medium heat and add the butter for the filling. When it has melted, add the spring onions and fry for a minute or so.
7. Add the peas and the mustard and cook for another minute, stirring. 
8. Add the milk and crème fraîche and gently simmer for 5 to 10 minutes until it thickens a little bit. Then add the cheese and give it a good stir.
9. When the cheese has melted, add the pieces of fish and cover them with the sauce. Stir in the chopped parsley and remove from the heat. Season with a little salt and pepper and stir again. 
10. Spoon the mash on top of the fish mixture and spread it out to cover the whole top. Use a fork to make a wavy patter on top to look like the ocean but don’t press too hard so you don’t push through.
11. Put the dish into the oven for 20 to 25 minutes until bubbling around the edges and crispy on top
12. Serve in bowls with extra veg on the side. How warming is that?